In-situ constructed indirect Z-type heterojunction by plasma Bi and BiO2-X–Bi2O2CO3 co-modified with BiOCl@Bi–MOF for enhanced photocatalytic efficiency toward antibiotics

Abstract

Currently, the chemical properties of metal–organic frameworks (MOFs) can be fully exploited by combining inorganic semiconductors with MOFs to improve their narrow light absorption range and high carrier separation efficiency. Therefore, in this paper, indirect Z-type multicomponent Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF heterojunction with plasma Bi and BiO2-X–Bi2O2CO3 co-modified with BiOCl@Bi–MOF were successfully prepared through combining hydrothermal and photodeposition methods using BiOCl@Bi–MOF composites as active carriers. The ability to remove chlortetracycline (CTC) with Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF was investigated by modulating the factors, such as photodeposition time, presence or absence of MOF structure, different water source, and different inorganic salts. In the CTC degradation experiments, the optimized Bi/BiO2-X–Bi2O2CO3/BiOCl@Bi–MOF-10-0.3 composite showed the best photocatalytic degradation efficiency (94.6%) within 90 min of full-spectrum light illumination. Its corresponding first-order kinetic rate constant (0.0315 min−1) was 2.5 and 1.6 times higher than those of MOF-free structural composites Bi/BiO2-X–Bi2O2CO3/BiOCl-10-0.3 and BiOCl@Bi–MOF, respectively. The increased photocatalytic activity is attributed to the synergistic effect between the MOF structure, metal Bi, BiO2-X–Bi2O2CO3, and BiOCl@Bi–MOF carrier. By combining the results of active species capture experiments, electron spin resonance techniques (EPR), and photoelectrochemical experiments, we have deduced a possible indirect Z-type heterojunction photocatalytic mechanism between Bi, BiO2-X–Bi2O2CO3 and BiOCl@Bi–MOF. The possible photocatalytic degradation pathways and products of CTC were deduced by combining liquid chromatography-mass spectrometry (LC-MS). This work supplies valuable guidance for preparing metal nanoparticles/semiconductor/MOFs with an indirect Z-type heterojunction photocatalyst for the repair of natural CTC wastewater.